Air-cleaning, heat-exchange apparatus

ABSTRACT

An air-cleaning, heat-exchange apparatus includes a main housing portion connected by means of an air inlet fan to the kitchen exhaust stack of a restaurant. The apparatus includes an in-line series of three heat exchangers through which a heat-absorptive fluid is circulated, simultaneously, by means of a suitable fluid pump. These heat exchangers remove exhaust gas heat and further transfer this heat to a stream of air, such as that from a cold-air return duct. Due to the fact that the hot exhaust gas is heavily grease laden, grease will be deposited on virtually all internal surfaces of the apparatus which this exhaust gas contacts. The apparatus includes means for spraying exhaust gas contacted internal surfaces, as well as the hot exhaust gas itself, with a detergent solution in which the grease is soluble, thereby removing grease buildup from these internal surfaces. Although some of the grease will be drained off by a liquid carrier resulting from the spraying at a first stage, any remaining emulsified grease, detergent solution and moisture will be eliminated from its gaseous carrier by means of a mist eliminator which is located downstream from the first stage.

BACKGROUND OF THE INVENTION

The present invention relates in general to air-cleaning apparata and inparticular to such apparata which also achieve heat exchange and heattransfer.

Industrial exhaust poses a major problem from the standpoint ofpollution, and with the promulgation of federal rules and regulationsand clean air standards, many efforts have been focused on how to reducethe level of contaminants from the effluent wastes. A related problemoccurs in the area of restaurant exhaust from areas such as grills andbroilers. Restaurants, especially fast-food restaurants, generate largeamounts of grease-laden exhaust from the frying and broiling of thevarious food items which are prepared. This grease-laden exhaust istypically drawn up through a kitchen hood and exhaust duct combinationto the atmosphere by a large ventilating fan arrangement. The problemwith this type of design is that the grease from the exhaust collects onthe internal surfaces of the hood, the exhaust duct and the fanarrangement and must be periodically cleaned. The frequency of requiredcleaning depends upon the volume of exhaust and the amount of grease,but a cleaning frequency of once a month is very often advisable inorder to assure that grease levels will not reach the point where a fireoccurring in the kitchen area will spread to and ignite this grease.Unfortunately, the thorough cleaning of the grease from the hood,exhaust duct and ventilating fan arrangement is difficult and is oftenquite time consuming and represents significant downtime to theparticular restaurant. As a result of the inconvenience represented bythe cleaning procedure, removal of the grease from the internal surfacesis not always performed when required. A somewhat predictableconsequence of this lack of proper and periodic cleaning is that thehood, exhaust duct and fan arrangement will become heavily grease coatedas well as producing a noticeable odor. Significant fire disasters haveoccurred where a grease fire in the kitchen exhaust duct was attributedto be a cause or at least a contributing factor to the spreading of thefire.

Recently efforts have been made to chemically treat such grease-ladenexhaust so that the grease is emulsified and its buildup on internalsurfaces is reduced. By using a mist-like spray of a chemical and watermixture directed around the inside of the exhaust duct between the hoodand ventilating fan, the emulsified grease is either drained off inliquid form or may be exhausted in vapor form. Although this method hasproved effective to prevent a majority of the grease buildup in theexhaust duct and on the ventilating fan, there remain certainshortcomings and disadvantages.

The spray arrangement just mentioned must have its volume of chemicalsolution governed by the volume of exhaust and the amount of grease, andto be effective, the sprayer must direct a mist against the full insideperimeter of the exhaust duct so that all surfaces can be cleaned ofgrease. This poses a very exacting requirement on the design of thespray nozzle head as well as its positioning within the exhaust duct.However, even with well designed and positioned spray nozzle heads, thegrease which is emulsified by the chemical solution spray does notrepresent 100 percent of the grease flowing through the exhaust duct andthe emulsified grease which is exhausted in vapor form, as well as thegrease which is not chemically treated, still contributes to thepollution of the atmosphere. Another very significant factor, especiallywith energy consideration concerns, is the amount of heat which isgenerated by the restaurant grills and broilers and is lost up theexhaust duct. Any attempt to capture this heat and reuse it for generalheating of the structure runs headlong into the related problems ofgrease accumulation. If a heat exchanger is employed, once theconvecting surfaces, such as the fins, collect a thin film of grease,the heat-transfer properties of such convecting surfaces are reduced tothe point that the heat exchanger becomes highly inefficient. Thisgrease buildup acts as a thermal insulator and prevents efficient heattransfer from the hot exhaust gas to a heat-absorptive fluid circulatingthrough the heat exchanger. Related problems involve how to extract amajority of this exhaust duct heat so that system efficiency is high andhow can the complete system be maintained in a virtually grease-freemanner while still not exhausting harmful pollutants (such as emulsifiedgrease) into the atmosphere. A collateral benefit of grease removal isthat the accompanying odor will also be eliminated. The shortcomings anddisadvantages discussed above are overcome by the apparatus of thepresent invention which is disclosed herein.

SUMMARY OF THE INVENTION

A heat-exchange apparatus incorporating contaminant removal means forextracting heat from a hot, gaseous flow stream while simultaneouslyremoving contaminant material from the hot, gaseous flow streamaccording to one embodiment of the present invention comprises athree-stage, heat-exchange arrangement centrally disposed within thehot, gaseous flow stream and includes first, second and third heatexchangers, a source of chemical solution, the contaminant materialbeing soluble in the chemical solution, chemical solution spray meansdirected toward the first heat exchanger for reducing buildup of thecontaminant material on the external surfaces of the first heatexchanger and a mist eliminator positioned in the hot gaseous flowstream between the first and second heat exchangers.

One object of the present invention is to provide an improvedexhaust-cleaning, heat-exchange apparatus.

Related objects and advantages of the present invention will be apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, perspective view of an exhaust-cleaning,heat-exchange apparatus according to a typical embodiment of the presentinvention.

FIG. 2 is a sectioned, end elevation view of the FIG. 1 apparatus astaken along line 2--2 in FIG. 1.

FIG. 3 is a sectioned, end elevation view of the FIG. 1 apparatus astaken along line 3--3 in FIG. 1.

FIG. 4 is a sectioned, end elevation view of the FIG. 1 apparatus astaken along line 4--4 in FIG. 1.

FIG. 5 is a fragmentary, partial plan view of one end of the FIG. 1apparatus.

FIG. 6 is a fragmentary, partial side elevation view of another end ofthe FIG. 1 apparatus as taken along line 6--6 in FIG. 4.

FIG. 7 is a schematic flow diagram of a fluid flow pattern associatedwith the FIG. 1 apparatus.

FIG. 8 is a block diagram of an exhaust gas flow path associated withthe FIG. 1 apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

Referring to FIG. 1, there is illustrated exhaust-cleaning,heat-exchange apparatus 20 which includes a main housing portion 21, afirst fan arrangement 22, a second fan arrangement 23 and a plurality ofdial indicators 24, 25, 26, 27 and 28 whose functions will be describedhereinafter. Main housing portion 21 includes a top skin 29 which isinsulated by a thickness of insulation 30 disposed on the inner surface,a lower skin 31 fabricated of expanded metal which is sealingly joinedto the lower perimeter edge of top skin 29 and a connecting duct portion32 which encloses the free end 33 of apparatus 20 between top skin 29and lower skin 31. An intermediate duct section (not shown in FIG. 1)connects second fan arrangement 23 with connecting duct portion 32 forstructural rigidity and an efficient flow pattern.

First fan arrangement 22 is sealingly joined at one flanged end ofarrangement 22 around a circular opening in top skin 29 at first end 36of apparatus 20. The opposite flanged end of first fan arrangement 22 issealingly joined around the perimeter of exhaust stack 37. Althoughexhaust stack 37 may represent virtually any suitable duct of astructure through which contaminant material is exhausted, typically ingaseous form, in the preferred embodiment exhaust stack 37 is theexhaust duct extending from a restaurant kitchen area and the hotexhaust gas which flows up through exhaust stack 37 is typically heavilygrease laden. Apparatus 20 includes a central flow passageway whichextends from first end 36 to opposite free end 33 and is enclosed by topskin 29 in combination with lower skin 31. Inasmuch as the circularopening in first end 36 represents the sole point of entry intoapparatus 20 for the hot exhaust gas from exhaust stack 37, apparatus 20which draws this hot exhaust gas into its interior by means of the twofan arrangements, functions as a closed system. As this hot exhaust gasflows through apparatus 20, heat is extracted by a series of heatexchangers while any grease which is deposited on the internal surfacesof apparatus 20 is removed by a chemical solution spray directed atthese internal surfaces. Consequently, the flow of exhaust gas which ispresent at end 33 is lower in temperature than the entering exhaust gasat end 36 and the grease which was contained within the entering exhaustgas is removed by the time the exhaust gas reaches free end 33. Theexhaust gas present at end 33 is pulled into the lower portion ofapparatus 20 by means of the second fan arrangement 23. As thisstill-warm exhaust gas passes into this lower region, which issurrounded by lower skin 31, a certain degree of heat will betransferred to the internal and surrounding portions of apparatus 20thereby providing a blanket of warm air and reducing the effect of aseverely cold temperature exterior to apparatus 20. This feature isimportant inasmuch as apparatus 20 is typically located on the roof of astructure and is exposed to all types of environmental conditions,including extremely cold temperatures. Due to the fact that one featureof apparatus 20 is the extraction of heat from the entering hot exhaustgas, it is important that heat losses to the atmosphere be reduced to asgreat a degree as possible. This warm, clean exhaust gas from free end33 assists in this heat loss reduction by acting as a buffer between theheat exchangers and the atmosphere.

In the operation of a restaurant kitchen, what typically occurs is thatgrease-laden exhaust from broilers and grills is drawn up through asuitable exhaust hood and duct arrangement by means of a suitableventilating fan. As the particles of grease which are within thisexhaust come in contact with the various internal surfaces of theexhaust duct and the ventilating fan, grease is deposited on thesesurfaces. After only a brief period of operation, the grease levelbecomes critical with respect to efficiency of the ventilating fan aswell as representing a potential fire hazard. The present inventionprovides an apparatus which is connectable to such an exhaust duct andprovides means by which grease buildup on internal surfaces may bevirtually eliminated while at the same time extracting heat from thishot exhaust gas which can be utilized to supplement some of the heatingrequirements for the structure with which apparatus 20 is associated.When apparatus 20 is employed, as will be described hereinafter, aventilating fan located within the exhaust stack is not requiredinasmuch as first fan arrangement 22 provides the necessary pullingdraft for removal of the exhaust from the kitchen area. First fanarrangement 22 sealingly joins to exhaust stack 37 in a suitable mannerwhich does not permit exhaust leakage. Surrounding first fan arrangement22 is a small cover portion 38 which connects to and completely aroundthe flange of the first fan arrangement 22 and also to top skin 29 so asto enclose first fan arrangement 22. The opposite flanged end of fanarrangement 22 sealingly joins to the circular opening in top skin 29 ashas been previously discussed. Located within top skin 29 is acylindrical drum member 39 (see FIGS. 2 and 4) which extends forapproximately one-half the overall length of apparatus 20 beginning atfirst end 36. The first end 40 of drum member 39 is located adjacentfirst fan arrangement 22 and drum member 39 is structurally arranged soas to be rotatable with respect to first fan arrangement as will bedescribed in greater detail hereinafter. By sealingly arranging flangedend 41 in alignment with first end 40 of drum member 39, virtually allthe hot exhaust gas which is drawn up through exhaust stack 37 will bepushed by first fan arrangement 22 into and through drum member 39.However, due to the fact that the drum member rotates with respect tothe fan arrangement a slight clearance is provided. Since this clearancepermits some leakage of the entering hot exhaust gas to occur, cover 38creates an enclosure which limits such leakage and prevents leakage tothe atmosphere.

Apparatus 20 further includes a structural frame fabricated fromaluminum angles and square aluminum tubing which is arranged so as toprovide four leg-like support members and a box-like structurethereabove. Although drum member 39 is positioned within the confines ofthis box-like frame structure, member 39 is thermally insulatedtherefrom and mechanically separated therefrom such that the entiresupport for drum member 39 with respect to the structural frame is bymeans of an arrangement of drive rollers and idle rollers. Drum member39 rests upon a pair of idle rollers 44 and 45 which are disposedbeneath drum member 39, rotatably fixed to the box-like frame structure,and adjacent end 40. Although only idle roller 44 is illustrated in FIG.4, it is to be understood that idle roller 45 is in line with idleroller 44 but on the opposite side of drum member 39. Drive rollers 46and 47 are disposed at the opposite second end 48 of drum member 39 andare rotatably fixed to their correspondingly adjacent portion of thebox-like frame structure. Rollers 46 and 47 act in combination with abelt drive and gear motor to provide rotation to drum member 39. Alsoadjacent second end 48 of drum member 39 are two additional idle rollers49 and 50 which provide a retaining and steadying feature to therotation of drum member 39 to rigidly hold drum member 39 in contactwith drive rollers 46 and 47 as well as drive belt 53 a portion of whichextends between drive rollers 46 and 47 and contacts the undersideportion of drum member 39. Drum member 39 includes a cylindrical metalbody portion 54, an outer layer of insulation 55, an inner end lipportion 56 which extends completely around first end 40 of drum member39 for retaining fluid which may collect within cylindrical body member54 and an exterior air seal 57 which rotates with drum member 39 andprovides additional sealing properties to prevent excess hot exhaust gasleakage. A guide roller 51 is provided at first end 40 for assisting incontrolling any longitudinal shift of drum member 39.

Disposed within cylindrical body member 54 of drum member 39 is a firstheat exchanger 58 which includes a first tapered, spiralled arrangement59 of copper tubing having its larger diameter end adjacent end 40 andwhich extends from a location adjacent end 40 to a second locationadjacent end 48. Heat exchanger 58 further includes a second tapered,spiralled arrangement 60 also of copper tubing which criss-crosses withthe first spiralled arrangement 59 in that the smaller diameter end ofarrangement 60 is adjacent end 40. The flow passageway through firstarrangement 59 and the flow passageway through second arrangement 60 aretied together at common points such that as a heat-absorptive fluid iscirculated through this copper tubing, heat transfer to theheat-absorptive fluid can be effected simultaneously from botharrangements. Consequently, as hot exhaust gas is pushed throughapparatus 20 by means first fan arrangement 22, a portion of the heatwithin this hot exhaust gas will be transferred to the copper tubingwhich in turn will conduct its absorbed heat to the circulatingheat-absorptive fluid passage therethrough. From this point, the hotexhaust gas, which is now at a somewhat lower temperature, passesfurther downstream through apparatus 20 where it flows across a misteliminator 61 and passes therethrough and then across a second heatexchanger 62 and after that through and across a third heat exchanger63. The structure and functions of the mist eliminator 61 and the secondand third heat exchangers 62 and 63 will be described in greater detailhereinafter. At this point, it should be understood that mist eliminator61 and heat exchangers 62 and 63 are located substantially central tothe flow stream of the hot exhaust gas.

Although the heat-exchange aspects of apparatus 20 may be viewed as of aconventional nature and known to the art, it is to be pointed out thatthe particular arrangement of drum member 39 which is thermallyinsulated as a unit as well as from the surrounding portions ofapparatus 20 provides a highly efficient heat transfer mechanism whereinheat losses to surrounding structural members or to the atmosphere aresignificantly reduced. The only contact which drum member 39 makes withthe surrounding box-like frame structure is indirectly through thevarious idle rollers and drive rollers. Since these rollers are coatedwith a rubber or synthetic compound, any heat transfer is negligible. Afurther feature which contributes to the overall efficiency to the heattransfer between the hot exhaust gas and the heat-absorptive fluid infirst arrangement 59 and second arrangement 60 is that the copper tubingof these arrangements is supported within drum member 39 by a minimalarea of metal-to-metal contact. This is achieved by the use of bracketbars 66 and 67 which are rigidly joined to their correspondingarrangements of copper tubing and are force-retained within cylindricalbody member 54 by means of bolts 68 which are threadedly received by thefree ends of the various bracket bars at the larger diameter end oftheir respective arrangements and are threadedly advanced into pressurecontact with the internal surfaces of cylindrical body member 54. Thereare four bracket bars 66 90 degrees apart associated with firstarrangement 59 and there are similarly four bracket bars 67 associatedwith second arrangement 60. There are various options available tosecurely position the two arrangements within body member 54, such as,for example, clamping together the crossing points of correspondingpairs of bracket bars 66 and 67.

As a result of this minimal metal-to-metal contact arrangement, any heatloss or heat transfer from the copper tubing to the metal surface ofcylindrical body member 54 must be through the bolts 68 and this minimalsurface area of contact means that a minimal amount of heat transferwill occur. As previously mentioned, the hot exhaust gas which arrivesthrough exhaust stack 37 is typically heavily grease laden. As thisgrease-laden exhaust gas flows up through exhaust stack 37, throughfirst fan arrangement 22 and then into drum member 39, portions of thisgrease will be deposited on all internal surfaces of apparatus 20 whichthe grease-laden exhaust gas comes in contact with. In order tocontinuously maintain apparatus 20 as a wet system, a feature whichgreatly contributes to fire prevention, and to prevent any greasebuildup from occurring on such internal surfaces, a chemical solutionsprayer arrangement is provided which communicates with a suitablesource of chemical solution for delivery into apparatus 20. Tubing line69 couples to a source 70 of chemical solution and extends upwardlyalong support leg 71 to which it may be attached by means of suitableclips or brackets. At the approximate base of first fan arrangement 22,tubing line 69 splits into two different branches by means of a suitabletee fitting 73. Branch line 74 extends from tee fitting 73 over and intoexhaust stack 37. The insertion of branch line 74 into exhaust stack 37is by means of a sealed connection and the free end of branch line 74 isprovided with a 160° spray nozzle head which is centrally positionedwithin exhaust stack 37 and is directed outwardly toward the internalsurfaces of exhaust stack 37 and upwardly toward first fan arrangement22. As chemical solution is delivered through branch line 74 to nozzlehead 75, a spray mist will be sprayed upon the internal surfaces ofexhaust stack 37. Inasmuch as a chemical solution is selected in whichthe particular exhaust gas contaminant, such as, in this case grease, issoluble; contact of the spray mist with grease which has collected onthese internal surfaces will cause the grease to go into liquid solutionin emulsified form. Although such liquid solution may initially draindown exhaust stack 37 back toward the kitchen area of the restaurant,the continuing upward flow of hot exhaust gas will convert thisemulsified grease-containing liquid into vapor form and will conduct iton through apparatus 20. Due to the fact that the grease has been brokendown and placed in a solution wherein it is soluble, this grease willremain in liquid solution and not be deposited on subsequently contactedinternal surfaces. However, the spray mist from nozzle head 75 is nottypically effective to place all of the grease flowing through exhauststack 37 into an emulsified condition due to the volume of exhaust andamount of grease. Consequently, some grease will be deposited on theinternal surfaces of drum member 39 including the first arrangement 59of copper tubing as well as the second arrangement 60 of copper tubing.However, the presence of spray nozzle head 75 at its location withexhaust stack 37 does provide sufficient cleansing action of theinterior surfaces of exhust stack 37 as well as a majority of the firstfan arrangement 22. This means that the exhaust stack 37 exiting fromthe kitchen portion of the restaurant will remain in virtually agrease-free status and will thereby preclude the presence of a firehazard due to grease collection.

In order to deal with grease buildup which occurs on the internalsurfaces of drum member 39 and the external surfaces of the first andsecond arrangements of copper tubing, branch line 76 extends upwardlyand then inwardly to the approximate center of the hot exhaust gas flowstream which coincides with the approximate geometric center of drummember 39 and first fan arrangement 22. At this point, branch line 76splits by means of a suitable fluid connection into spray nozzle heads77 and 78 which are directed inwardly toward drum member 39 andoutwardly toward the internal surfaces of cylindrical body member 54.These two spray nozzle heads are disposed on opposite sides of thecylindrical axis of drum member 39 in a generally symmetrical manner.The angular spray direction of each nozzle head as well as the angularseparation between spray nozzle head 77 and spray nozzle head 78 may bevaried, depending upon the particular size of drum member 39, the volumeof exhaust gas, the amount of grease, and the rate at which drum member39 is rotated. It is important to note that spray nozzle heads 77 and 78are stationary with respect to main housing portion 21 and will create afixed spray pattern with respect to the interior of drum member 39. Asthis chemical solution spray originating from source 70 is generatedthrough nozzle heads 77 and 78, it will contact portions of the externalsurfaces of first arrangement 59 and second arrangement 60 as well asportions of the internal surface of cylindrical body member 54. Thischemical solution spray places the grease which it contacts into anemulsified state. Some of this emulsified grease will be collected inthe lower portion of body member 54 in a liquid carrier resulting fromthe excess spray liquid, and some will be placed into vapor form by theaction of the hot exhaust gas which continues to flow through apparatus20. This flowing hot exhaust gas is also effective to carry portions ofthe chemical solution spray to other regions of the drum member downstream from the location of spray nozzle heads 77 and 78. In thismanner, virtually all areas of drum member 39 and arrangements 59 and 60will receive a portion of the chemical solution spray mist. Inasmuch asspray nozzle heads 77 and 78 are stationary, it is not guaranteed thatall areas of drum member 39 will be contacted due to inherent designinefficiencies in nozzle designs and positioning. For this reason, drummember 39 rotates at approximately one revolution per minute so that allregions can be guaranteed contact with the chemical solution spray mist.The grease removal from the external surfaces of first arrangement 59and second arrangement 60 insure that high heat transfer efficiency willbe maintained and that an insulating layer of grease will not bepermitted to build up on these surfaces which would significantly reduceheat transfer.

Grease from within drum member 39 which is placed into a liquid mixturewith the chemical solution will accumulate in the lowest level of drummember 39 and a drain outlet 79 is provided by which this liquid mixturemay be removed from within drum member 39. Drain outlet 79 opens into afunnel member 80 which connects to drain tube 81 which ultimately flowsto the drain system of the structure. It is possible for this grease andchemical solution mixture to congeal in the event the surroundingtemperature is sufficiently low. Inasmuch as warm air is introducedbeneath drum member 39 by means of second fan arrangement 23, theportion of drain tube 81 which is interior to apparatus 20 will remainwarm enough so that the grease mixture will not congeal. However, whendrain tube 81 exits from apparatus 20 on its way to the drain system ofthe structure, electrical tape 82 is wrapped around drain tube 81thereby providing sufficient heat to retain the grease and chemicalsolution mixture in liquid form.

The emulsified grease which remains in vapor form as part of the hotexhaust gas will be circulated through drum member 39 and out end 48.Adjacent to end 48 of drum member 39 is a mist eliminator 61 (see FIGS.4 and 5) which includes a plurality of evenly spaced tortuouspassageways through which the exhaust gas must flow. These variouspassageways are separated by corrugated panels which have a plurality ofrib-like hooks which alternately protrude from one side of each paneland then the other side. A suitable mist eliminator for this particularapplication is a model 921-22 offered by the Heil Process EquipmentCompany of Cleveland, Ohio. Panels 85 are thin-walled members measuringapproximately 0.040 to 0.050 inches in thickness and the hooks 86 arespaced along the panels approximately every four inches. Such a misteliminator is effective to remove approximately 99 percent of the liquidcontent of the gaseous flow which passes across and through the misteliminator 61. This is the final stage which removes virtually allremaining grease from the exhaust gas circulating through apparatus 20.By taking the emulsified grease out of vapor form and converting it backinto a liquid mixture, this being performed by mist eliminator 61, thisremaining grease is able to be drained out of apparatus 20 by means ofinclined drain pan 87 and drain tube 88 which couples to drain tube 81by means of a suitable fluid connection. Now that virtually the entiregrease content of the hot exhaust gas has been removed as well as aportion of the heat having already been extracted by means of first heatexchanger 58, subsequent heat removal can occur. This is accomplished bysecond heat exchanger 62 and then by third heat exchanger 63. Arrows 89represent the flow path of the hot exhaust gas which exits from misteliminator 61. This flow path is through second heat exchanger 62 whichis constructed in much the same manner as an automobile radiator. Secondheat exchanger 62 includes a plurality of closely-spaced fin members 90through which this hot exhaust gas is permitted to flow. Running in adirection normal to this gas flow direction is a length of tubing whichwinds back and forth through second heat exchanger from one end to theother. A heat-absorptive fluid is provided to this length of tubing bymeans of fluid inlet 91. This heat-absorptive fluid is permitted tocirculate through second heat exchanger 62 in that a return fluid outlet92 is also provided at the opposite end of the length of tubing fromfluid inlet 91. The exhaust gas flow which passes through and exits fromsecond heat exchanger 62 will thereafter enter heat exchanger 63 andwill have an exhaust gas flow therethrough as indicated by arrows 95.Third heat exchanger 63 is also arranged with a plurality of fin members96 and a length of tubing extending through heat exchanger 63 in adirection normal to arrows 95 and is connected between fluid inlet 97and fluid outlet 98. Inasmuch as the exhaust gas flow through secondheat exchanger 62 has a maximum volumetric capacity, an alternate orescape route is also provided for exhaust gas flow which exceeds thatmaximum of heat exchanger 62. This alternative exhaust gas escape path99 extends along the face of second heat exchanger 62 and around oneend. From this point, this escape path extends between second heatexchanger 62 and third heat exchanger 63 to the opposite end of heatexchanger 63. At this point, the exhaust gas flowing through the escapepath joins with that exhaust gas which has passed through third heatexchanger 63 and this combined flow is drawn down through connectingduct 32 into second fan arrangement 23. An intermediate duct section 100is provided as an interface between connecting duct 32 and second fanarrangement 23. This intermediate duct section 100 is provided forstructural and fabrication convenience in that it is rigidly secured toone flanged end of second fan arrangement 23 and joins with connectingduct 32 at its opposite side.

By the time the exhaust gas reaches second fan arrangement 23, all theheat which can be extracted has been extracted. Furthermore, the greasebuildup within apparatus 20 as well as within exhaust stack 37, has beenconverted into a liquid mixture with the chemical solution and has beendrained off to the drain system of the structure. The gaseous flowreaching second fan arrangement is still relatively warm and is nowquite clean. This gaseous flow is directed across the lower portion ofapparatus 20 for the providing of a heating blanket of air which hasbeen previously mentioned.

This lower portion of apparatus 20 includes a structural shelf 103 whichis supported on opposite sides by shelf brackets 104 and 105 which arebolted to adjacent frame leg members. Supported on structural shelf 103are the various drive components for the drum member rotation and thecirculation of the heat-absorptive fluid through the three heatexchangers. Drive motor 106 is an electric gear motor which ismechanically coupled by means of pulley 107 and drive belt 53 to driverollers 46 and 47 which create a friction drive with drum member 39 aspreviously described. A suitable motor for drive motor 106 is a model3M126A offered by Dayton Electric Manufacturing Company of Chicago,Illinois. Also located on structural shelf 103 at a position forward ofdrive motor 106 is an AC motor 108 which drives fluid pump 109. AC motor108 is mechanically coupled to fluid pump 109 by means of a suitablearrangement of pulleys 110 and 111 and belt 112. A suitable motor for ACmotor 108 is a model 5KC37NN3 offered by the General Electric Company.Also arranged as part of this lower portion of apparatus 20 aredeflector plates 115 and 116 which are utilized to baffle and direct theflow of hot exhaust gas which exits from second fan arrangement 23across structural shelf 103. These deflector plates permit a moreuniform distribution of this hot exhaust gas so that all areas withinapparatus 20 may be uniformly heated for a corresponding reduction oftemperature gradient with the external atmosphere.

The first fan arrangement 22 and the second fan arrangement 23, althoughoppositely located, are driven in a similar manner. Although second fanarrangement 23 will be described in detail, the same is to be understoodas applicable to first fan arrangement 22. The structural location andsupport of second fan arrangement 23 has previously been described. Inthat arrangement, a drive motor 117 is rigidly mounted to one of theframe leg members of the box-like frame structure for apparatus 20. Thisdrive motor is mechanically coupled to second fan arrangement 23 bymeans of a suitable pulley 118 and continuous belt 119. In order topreserve proper belt tension between second fan arrangement and drivemotor 117, drive motor 117 is rigidly secured to an intermediate platemember 120 which is arranged so as to slide inwardly or outwardly withrespect to the structural frame leg member so that the length of belt119 can be altered as is necessary. A similar arrangement is providedfor drive motor 121 which is associated with first fan arrangement 22.

The use of first fan arrangement 22 in combination with second fanarrangement 23 provides a unique concept in that first fan arrangement22 acts in a pushing manner, pushing the hot exhaust gas through thedrum member 39. However, second fan arrangement 23 acts in a pullingmanner, pulling the hot exhaust gas through drum member 39. The effectis that there is a zero pressure level created within the drum member inthat there is neither an excess pressure nor a vacuum created and thiscontributes to the evenness and uniformity of the flow pattern throughand across the various heat exchangers. This is desirable from thestandpoint of maximum efficiency and uniform heat transfer. A suitabledevice for both first fan arrangement 22 and second fan arrangement 23is a Dayton model 7C411 offered by W. W. Grainger, Inc. Inasmuch as amodel 7C411 fan is operable at either 1,150 RPM or 1,725 RPM with a freeair flow rate of 4,000 CFM, it is possible to create any one of eightdifferent combinations of fan utilization by means of either turning onefan arrangement off or on and if on at one of its two speed settings. Afurther feature associated with first fan arrangement 22 involves therelative diameter sizes of exhaust stack 37 with respect to cylindricalbody member 54 of drum member 39. Exhaust stack 37 measuresapproximately 12 to 14 inches in diameter while cylindrical body membermeasures approximately 18 inches in diameter. Consequently, when the hotexhaust gas flowing through exhaust stack 37 enters cylindrical bodymember 54, its flow velocity will be significantly reduced in proportionto the cross-sectional area of these diameter measurements. This reducedexhaust gas speed flow means that heat transfer to the first and secondarrangements of copper tubing of the first heat exchanger will beenhanced. If the exhaust gas flow speed was too fast, a greater portionof the heat would pass through to second fan arrangement 23 and wouldnot be able to be utilized for the heat transfer by means of the variousheat exchangers.

Referring to FIG. 7, the flow pattern of the heat-absorptive fluid isillustrated. Returning heat-absorptive fluid which is at a relativelylow temperature is introduced into apparatus 20 at point 125. Cut-offvalves 126 and 127 are provided on either side of fluid pump 109. Asuitable fluid pump for this application is a model 1P830 offered byTeel Manufacturing Company of Chicago, Illinois. This fluid pumpoperates at approximately 1,200 RPM and provides approximately 10gallons per minute. Dial indicator 24 indicates the temperature of thisincoming heat-absorptive fluid and after indicator 24, the flow pathsplits into three separate branches. The first branch 128 suppliesheat-absorptive fluid to first heat exchanger 58 which is located withindrum member 39. Rotary joints 129 and 130 are provided so that the firstheat exchanger is able to rotate with drum member 39 while theconnecting fluid tubing remains stationary. Second branch 131 couples tosecond heat exchanger 62 while third branch 132 couples to third heatexchanger 63. The return lines 128a, 131a and 132a connect at commonpoint fitting 135 where they reunite into a single flow path. Dialindicator 25 indicates the temperature of this heat-absorptive fluidafter heat transfer from the hot exhaust gas to this heat-absorptivefluid has occurred simultaneously within the three different heatexchangers. This single flow path indicated by pipe 136 extends to aremote location where it couples to additional heat exchangers. Suchheat exchangers may be a finned arrangement located in combination withthe cold air return duct of the conventional heating system for theparticular structure. In this manner, the hot heat-absorptive fluid inflow pipe 136 will be transferred to these remote heat exchangers atwhich point heat transfer from the heat-absorptive fluid to the passingcold air will take place and will provide heat to the interior of thestructure as a supplement to the conventional heating system. A point ofsplit 137 is illustrated in FIG. 7 as representative of the flow splitfrom flow pipe 136 when a plurality of remotely located heat exchangersare involved. The remaining dial indicators 26, 27 and 28 indicate thetemperature of the entering hot exhaust gas, the temperature of theexhaust gas as it leaves second fan arrangement 23 and the fluidpressure being pumped through the various heat exchangers.

Referring to FIG. 8, a block diagram is provided of the exhaust gas flowthrough apparatus 20. The first stage is through the first fanarrangement 22. From that point, the hot exhaust gas is passed throughand across first heat exchanger 58 which has fluid flow linescommunicating therewith. After first heat exchanger 58, the hot exhaustgas which now has had a portion of the grease removed therefrom as wellas a portion of its heat, flows through mist eliminator 61 whichextracts the remaining vapor within this gaseous flow. After misteliminator, the exhaust gas flows through and across second heatexchanger 62 which also includes fluid connections communicatingtherewith and from there to third heat exchanger 63 also including fluidconnections communicating therewith. The final stage of flow for theexhaust gas is through the second fan arrangement and then into thelower portion of apparatus 20.

A further feature of apparatus 20 is illustrated by FIG. 6 which showsin fragmentary form the mounting of first fan arrangement 22 onto thefirst end 40 of apparatus 20. As previously described, apparatus 20includes a structural frame portion which includes a series of aluminumangles and square aluminum tubing rigidly secured together. Thesestructural frame members are indicated as upright frame members 138 andcross members 139. Inasmuch as these frame members provide a box-likeframe structure into which drum member 39 is located, there remaincorner areas disposed at the first end of member 39 which create aninefficient arrangement. Consequently, a skin sheet 140 having acircular opening therein which is slightly larger than the diameter ofcylindrical body member 54 is rigidly attached over first end 40. Bondedto the outer surface of this skin sheet 140 are a plurality of strips141 of rubber material. These strips 141 are arranged in a generallyframe-like orientation substantially coincident with frame members 138and 139. On top of these rubber strips 141 the flange 142 at flanged end41 of first fan arrangment 22 is rigidly attached through strips 141into frame members 138 and 139 and is secured thereto by means of threebolts 143. The fourth point of attachment of flange 142 to frame member138 and 139 is by means of pivot pin 144. Once the fan arrangement 22 isdiscconnected from exhaust stack 37 and the three bolts 143 are eachremoved, first fan arrangement 22 is permitted to pivotally swingdownwardly and out of the way of drum member 39 by means of pivot pin144. This is desirable in the event spray nozzle heads 77 and 78 wouldneed to be adjusted, repaired or replaced. Similarly, the first fanarrangement can be pivotally swung out of the way in the event minorrepair, cleaning or other overhaul related work is desired to beperformed on apparatus 20.

It can be seen then that what has been described by the foregoingdescription is a modular unit which can conveniently tie into anexisting exhaust stack of a structure such as a restaurant. The variousutility connections of apparatus 20 can be accomplished in a somewhattypical manner. Power box 147 is provided on the side of apparatus 20for coupling the requisite electrical power to the various motorsassociated with apparatus 20. Similarly, drain tube 81 can be routed tothe drain system of the structure and the entire unit can be rigidlysecured to a rooftop level. By providing source 70 of chemical solutionas part of apparatus 20, a minimum of fluid connections external toapparatus 20 are required. It should be noted, however, that source 70of chemical solution may also include as part of it a supply of water150 such that once the chemical solution is sprayed onto the internalsurfaces of apparatus 20 and begins the emuslifying of the grease, thata water rinse may be desirable to flush away this emulsified grease inliquid form. Although various chemical solutions can be used, theselection of which solution depends upon the nature of the contaminantwhich is within the exhaust stream. A major contaminant material isbelieved to be grease as has been described, however, other contaminantsubstances can be removed from their corresponding gaseous flow streamby the selection of a proper chemical solution in which the particularcontaminant material is soluble. A further feature is that the chemicalsolution need not be sprayed in a continuous manner but rather issprayed in a pulsating manner. This permits the chemical solution to besprayed onto a particular area of apparatus 20 and then remain therewhile its chemical action operates on the grease buildup. Then, a timeinterval later, a rinse of water is also pulsated across this same areathereby rinsing away the emulsified grease. In the preferred embodiment,water is pulsated in an on and off spray manner for approximately 50minutes out of each hour. This pulsating spray mist of water is on forapproximately 30 seconds and is then off for a corresponding 30 seconds.At the end of a 50-minute time interval, a chemical solution, such as adetergent, is pulse-sprayed in 30-second on and 30-second off intervalsfor approximately 10 minutes. This procedure conserves the chemicalsolution yet provides a sufficient amount for the emulsifying of thegrease without excess and waste. Similarly, the mist sprayed is so finethat only approximately four gallons of water are used per hour. Byhaving a continuously pulsating spray of water or chemical solution, theentire system is maintained in a wet condition. This means that firestarting is quite unlikely for two reasons. The first reason is thatgrease buildup is virtually eliminated from within apparatus 20 and thesecond reason is that the internal portions of apparatus 20 remain in awet condition.

Although hot exhaust gas has been referred to, it is to be understoodthat the air-cleaning, heat-exchange apparatus disclosed herein alsofinds applicability as a cooling apparatus. In lieu of hot exhaust gas,consider any gaseous flow from a structure, such as ambient air, whichhas a temperature higher than the temperature of the heat-absorptivefluid circulating through the various heat-exchange means. A coolingcoil in communication with the heat-absorptive fluid will provide asufficient temperature difference for this application. Heat transferwill occur thereby resulting in a gaseous flow output from apparatus 20which has a lower temperature than the entering flow. This output flowcould then be introduced back into the structure for cooling. Duringthis cooling mode of operation, the gaseous flow may still be chemicallytreated as has been described in order to remove any contaminants andespecially odors from the ambient air.

A further feature of apparatus 20 is that the heat transfer (heatrecovery) aspect of operation and the contaminant-removal aspect ofoperation are separate and distinct operational modes. The heat recoverymode may be used selectively as an option, while the contaminant removal(cleaning mode) goes on continuously with the operation of apparatus 20.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. An air-cleaning, heat-exchange apparatus havingmeans defining a flow path for removing grease and extracting heat fromgrease-laden, hot exhaust of a restaurant exiting from said restaurantby way of an exhaust stack, said air-cleaning, heat-exchange apparatuscomprising:a spiralled arrangement of metal tubing disposed in the flowpath of said hot exhaust and rotatable about an axis which issubstantially parallel with the flow direction of said hot exhaust, saidspiralled arrangement being adapted for circulation of a heat-exchangeworking fluid therethrough and the exterior of said spiralledarrangement providing a contaminant-collecting surface; means forcirculating a heat-exchange working fluid through said spiralledarrangement and between said spiralled arrangement and a location ofutilization; a source of chemical solution wherein the grease of saidgrease-laden, hot exhaust is soluble to said chemical solution; spraynozzle means directed at a first end of said spiralled engagement ofmetal tubing for dissolving grease buildup on the external,contaminant-collecting surface of said spiralled arrangement of metaltubing, said first end being disposed for being first contacted by theflow of said hot exhaust, and pump means for providing pulses of saidchemical solution to said spray nozzle means.
 2. The apparatus of claim1 which further includes a first fan arrangement disposed within theflow path of said hot exhaust between said restaurant and saidarrangement of metal tubing.
 3. The apparatus of claim 2 wherein saidarrangement of metal tubing being rotated at a speed of between 0.90 and1.10 RPM and said spray nozzle means being stationary.
 4. The apparatusof claim 3 which further includes additional heat-exchanger meanslocated in said flow path of hot exhaust subsequent to said arrangementof metal tubing.
 5. The apparatus of claim 4 which further includes amist eliminator disposed in said flow path of hot exhaust between saidadditional heat exchanger means and said arrangement of metal tubing. 6.The apparatus of claim 5 which further includes an inlet sprayerarrangement located in the exhaust stack of the restaurant between saidrestaurant and said first fan arrangement, said inlet sprayerarrangement being designed and arranged to provide a pulsating spray ofsaid chemical solution against the sides of said exhaust stack in adirection toward said first fan arrangement.
 7. An air-cleaning, heattransfer apparatus for removing contaminant material from an air flowfrom a structure while effecting a temperature change to the air flow,said air-cleaning, heat-transfer apparatus comprising:a main housingportion having an inlet end for receiving said air flow from thestructure and an outlet end for returning said air flow to thestructure; a rotatable drum-like member disposed within said mainhousing portion; a heat-transfer, contaminant-collecting tubingarrangement secured within said rotatable drum-like member and rotatablewith said rotatable drum-like member relative to said main housingportion; fluid-circulating means for circulating a heat-transfer fluidthrough said heat-transfer, contaminant-collecting tubing arrangementfor heat transfer with said air flow; sprayer means arranged within saidmain housing portion and being directed toward said heat-transfer,contaminant-collecting tubing arrangement for spraying acontaminant-soluble chemical solution onto said heat-transfer,contaminant-collecting tubing arrangement for removing contaminantbuildup therefrom, said sprayer means being stationary relative to saidmain housing portion; and drive means coupled to said heat-transfer,contaminant-collecting tubing arrangement for creating rotary motion ofsaid heat-transfer, contaminant-collecting tubing arrangement.
 8. Anexhaust-cleaning, heat-exchange apparatus for removing contaminantmaterial from a hot exhaust gas from a structure exhaust stack and forextracting heat from said hot exhaust gas, said exhaust-cleaning,heat-exchange apparatus comprising:a main housing portion adapted forcommunication with said structure exhaust stack; a rotatable drum-likemember disposed within said main housing portion; a spiralled tubingarrangement disposed within and rigidly attached to said rotatabledrum-like member, said spiralled tubing arrangement adapted forcirculation of a heat-exchange working fluid therethrough and theexterior of said spiralled tubing arrangement providing acontaminant-collecting surface; sprayer means arranged within said mainhousing portion and directed toward said contaminant-collecting surfaceand toward the interior surface of said rotatable drum-like member forspraying a chemical solution from a suitable source onto saidcontaminant-collecting surface and onto said interior surface, saidcontaminant material being soluble to said chemical solution; fluidcirculating means for circulating a heat-exchange working fluid throughsaid spiralled tubing arrangement; and a first fan arrangement incommunication with and disposed between said main housing portion andsaid exhaust stack for routing said hot exhaust gas across saidspiralled tubing arrangement whereby heat is transferred from said hotexhaust gas to said circulating heat-exchange working fluid.
 9. Theapparatus of claim 8 which further includes a plurality of heatexchangers arranged substantially central to the flow of said hotexhaust gas through said main housing portion and disposed subsequent tosaid spiralled tubing arrangement, whereby said spiralled tubingarrangement is positioned between said plurality of heat exchangers andsaid first fan arrangement.
 10. The apparatus of claim 1 wherein saidsprayer means includes a plurality of spray nozzles disposed adjacentone end of said rotatable drum-like member for spraying said chemicalsolution, said nozzles being stationary relative to said main housingportion.
 11. The apparatus of claim 10 wherein said sprayer meansfurther includes an inlet sprayer positionable within said exhaust stackand suitably arranged for spraying said chemical solution onto theinside surface of said exhaust stack.
 12. The apparatus of claim 9 whichfurther includes a mist eliminator positioned in said main housingportion between said spiralled tubing arrangement and said plurality ofheat exchangers.
 13. The apparatus of claim 12 which further includes asecond fan arrangement in communication with said main housing portion,said first fan arrangement being operable for pushing said stream of hotexhaust gas through said main housing portion, said second fanarrangement being operable for pulling said stream of hot exhaust gasthrough said main housing portion.
 14. The apparatus of claim 13 whereinsaid drum-like member being coupled to friction drive means and rotatedat a speed of less than two RPM.